1. Field of the Invention
The present invention relates generally to the support of vehicles, and more particularly to a system of leveling and supporting trailers, campers, motorhomes, trucks and other vehicles in a level position while parked on uneven or sloping terrain.
2. Description of the Prior Art
It has been proposed in the past to provide various types of systems and devices for use in leveling and supporting a vehicle on uneven on sloping terrain. Such systems have included hydraulic jacks which are mounted on the bottom of the vehicle and which are pivoted to swing from a horizontal storage position to a vertical operating position prior to use. Representative of such prior proposals are the following patents:
U.s. pat. Nos. PA1 French Pat. Nos.
4,061,309--Hanser PA2 4,050,718--Newcomb PA2 3,989,277--Stahl PA2 3,817,493--Hanser PA2 2,546,203--Tucker PA2 2,442,881--Soskin PA2 625,003--Gomez PA2 729,257--Marion
Of these patents, U.S. Pat. Nos. 2,442,881 and 2,546,203 and the two French patents, are quite similar in structure and function. Each suggests a jack assembly having two hydraulic cylinders (or equivalent). The plunger of the first cylinder is extended not only to rotate the jack assembly into operating position but to expose an outlet through which fluid is directed to the second cylinder for extension of the second plunger. This outlet, of course, must remain open to permit later retraction of the second plunger. Thus, in the event of inadvertent movement of a vehicle having jack assemblies of the type suggested by these patents, excess pressure in either cylinder would keep the plunger of the other cylinder extended, leading to the likelihood of severe damage to the jack assemblies, the vehicle, or both.
U.S. Pat. No. 3,817,493 teaches an assembly having linkage which swings the jack down as the piston is extended. Particularly if the space below a vehicle should be quite limited, the piston in this type of structure may not be able to extend sufficiently to rotate the jack into proper operating position before contacting the ground. This could lead to improper and somewhat unstable vehicle support. Also, the linkage mechanism disclosed in this patent is susceptible to certain problems of possible malfunction should ice or dirt build up thereon.
U.S. Pat. Nos. 3,989,277 and 4,050,718 are directed to devices quite far removed from the present invention, but are cited as illustrative of other types of support systems that have been proposed. U.S. Pat. No. 3,989,277 teaches a simple manually operated screw type jack arrangement, and U.S. Pat. No. 4,050,718 an arrangement wherein the leveling jacks are rotated into position by movement of the vehicle to be supported. The first arrangement, of course, makes no provision for inadvertent movement of the vehicle, whereas the latter system obviously would be unstable and insecure.
U.S. Pat. No. 4,061,309, teaches a device for use in a leveling system wherein two hydraulic cylinders are extended in sequence to rotate the support assembly into operating position and then engage the ground. The arrangement shown in this patent overcomes the several problems discussed above relative to the other prior art, but the fluid by-pass arrangement through the first cylinder is relatively complicated and expensive both to manufacture and maintain.